I would buy a gallon of EvapoRust and soak the front bumperettes in for a few hours. Then rinse / dry, then spray the back side, with Rustoleum Reformer. ( Bonds to rust makes it sleep )..then paint with silver hammer rite. Those bumperettes will be very hard to come by very soon. Your bumper you should spray the back with Reformer it bonds to surface rust. Then spray with Silver Hammerite. It's very tough paint ,in a spray can. Will keep your bumper from any more rust from the back. The front outside chrome surface of the bumper clean with Blue metal polish. Then use meguires Cannuba wax . Often . Because chrome is not a solid finish it's a porous finish by keeping wax filling all the micro pores you save your bumper from getting worse it will stay as it is.
